Impacting device

ABSTRACT

The impacting device is primarily intended for rock drills and consists of a drive piston, a hammer piston and an auxiliary piston, wherein the drive piston drives the hammer piston by means of an elastic fluid cushion. The powertransmitting fluid cushion obtains a very high working pressure by being fed with elastic fluid under pressure and by being compressed by the drive piston during its working stroke. The auxiliary piston stops the hammer piston during its return stroke by absorbing the kinetic energy of the hammer piston. The hammer piston is stopped in a predetermined position corresponding to the optimum energy output before the succeeding stroke.

United States Patent [191 Erma [ IMPACTING DEVICE [75] Inventor: Eero Antero Erma, Klinten, Sweden [73] Assignee: Atlas Copco Aktiebolag, Stockholm,

Sweden 22 Filed: Nov. 3, 1970 21 Appl. No.: 86,467

[30] Foreign Application Priority Data Nov. 7, 1969 Sweden 15297/69 [52] US. Cl. 60/563, 91/234, 173/1 l6,

[51] Int. Cl. FlSb 7/00, F01121/02, E2lb 1/00 [58] Field of Search 91/234, 235; 60/625, 62.6, 54.5, 54.6 H, 54.5 HA, 54.6

HA, 54.5 A, 54.6 A; 173/116, 139

[ Aug. 28, 1973 891,831 6/1908 Frederick 91/234 543,052 7/1895 Rinsche 91/234 FOREIGN PATENTS OR APPLICATIONS 734,207 8/1941 Germany 173/139 Primary Examiner-Martin P. Schwadron Assistant Examiner-A. M. Zupcic Attorney-Munson and Fiddler [5 7] ABSTRACT The impacting device is primarily intended for rock drills and consists of a drive piston, a hammer piston and an auxiliary piston, wherein the drive piston drives the hammer piston by means of an elastic fluid cushion. The powertransmitting fluid cushion obtains a very high working pressure by being fed with elastic fluid under pressure and by being compressed by the drive piston during its working stroke. The auxiliary piston stops the hammer piston during its return stroke by absorbing the kinetic energy of the hammer piston. The hammer piston is stopped in a predetermined position corresponding to the optimum energy output before the succeeding stroke.

3 Claims, 2 Drawing Figures Pate hted Aug. 28, 1973 2 Sheets-Sheet 1 Ill/IT Fig.1

EERO ANTERO ERMA INVENTOR.

MUNSON & FIDDLER,

Attorneys.

Patented Aug. 28, 1913 3,754,396

2 Sheets-Sheet 2 Fig. 2

HERO ANTERO ERMA INVENTOR.

Y MUNSON & FIDDLER,

Attorneys.

IMPACTING DEVICE This invention relates to an impacting device for instance for rock drills, comprising a housing wherein a drive piston and a hammer piston, driven by the drive piston, are reciprocably guided.

The invention intends to provide a reciprocating motor, having a great driving force and high frequency. These intentions of the invention are obtained by the characteristics stated in the claims.

The invention is further described with reference to the accompanying drawings wherein FIG. 1 shows a longitudinal section of a reciprocating motor according to the invention, which motor is built together with an impacting device, for instance for a rock drill.

FIG. 2 shows a longitudinal section of a modified motor built together with an impacting device.

The machine shown in FIG. 1 is constructed in accordance with the invention and is intended for rock drilling and the like. It consists of two main parts, namely a pressure fluid driven motor 1 and and impacting device 2 both of which are located within a common housing 3.

The motor 1 consists of a cylinder 4 in which a piston 5 is reciprocably guided. The piston is thin walled and defines a chamber 6. This chamber 6 is supplied with the driving fluid of the motor from a pressure fluid source. The driving fluid is gaseous and consists preferably of air. (To simplify the terminology the machine will be described in the following with air as driving medium).

At both ends, the piston 5 is provided with end parts 7 and 8, which are coaxial with and of less diameter than the main part of the piston. The end parts 7 and 8 are guided in extensions 9 and 10 of the cylinder 4. One of the end parts is open at its outer end constituting a tubelike extension of the piston. The corresponding extension 9 of the cylinder 4 is directly connected to a pressurized air conduit by means of a nipple 11. The other end part 8 of the piston 5 is closed at its outer end constituting a drive piston for the impacting device. The cylinder 4 and the piston 5 defines annular chambers 12a, 12b at the ends of the main part of the piston. These chambers are intended to be supplied with pressurized air for driving the piston during it power stroke and return stroke. They are also intended to provide air cushions by means of which the piston is recoiled in its end positions.

To distribute pressurized air to the two cylinder chambers the piston and cylinder walls are provided with openings 13 and 14-17 respectively and distributing channels 18-19. The cylinder 4 is also provided with exhaust openings 20-21. These openings are covered and uncovered by the piston 5 during its movement in the cylinder, so that pressurized air, via the distributing channels, always is distributed to the proper side of the piston to reciprocate it in the cylinder. In the drawing there is shown only one of each of the openings and the distributing channels, but there is in fact a number of them distributed over the piston and the cylinder circumferences.

As the piston 5 moves in the clyinder 4 towards one of its end positions, which is shown as the upper in FIG. 1, the order of operation is as follows:

At first the front edge of the piston covers the exhaust opening 20. Then the openings 13 and register with each other so that pressurized air can flow from the chamber 6 within the piston, through the distributing channel 18 and the opening 14 into the chamber 12a. The chamber 12a is thus pressurized. Subsequently the front edge of the piston covers the opening 14 sealing the chamber 12a. An air cushion by means of which the piston is being slowed down, thus is entrapped in this chamber. The air cushion is then compressed. Owing to the elasticity of air, the air cushion has now an inherent expansion power which recoils the piston in the opposite direction. Thus, the piston 5 is recoiled at its end position by means of an air cushion with a velocity in the opposite direction. Firstly, while moving in the opposite direction, the piston will uncover the opening M. At this moment the air cushion will have recovered its original volume and its pressure will be reduced to the original level or to the same pressure as in the distributing channel 18 and the chamber 6. The pressurized air in the chamber 6 can now drive the piston 5 downward. Finally, the connection between the chamber 6 and the distributing channel 18 is broken and after some expansion of the air within the chamber 12a the exhaust opening 20 is uncovered so that the pressurized air in the chamber 12a may escape into the atmosphere. The above described order of operation is repeated every time the piston 5 is changing direction.

As the piston 5 is reciprocated by means of the air cushions, the stresses within the piston are considerably reduced. That means that the piston can be made with thin walls and be comparatively light. Consequently the piston can be made with a large cross sectional area without increasing the piston weight. The piston may preferably be made of a light metal alloy. Owing to the low piston weight and to the fact that the piston recoiled by means of air cushions at the end positions, the motor can be working with a very high frequency. Another factor which has a determining influence on the frequency, is the chamber within the piston, which will serve as a surge chamber, one problem in increasing the frequency or impacting rate of a motor of this type is to feed the cylinder chambers with driving fluid at a sufi'iciently high rate of speed. This fluid must have a very high velocity during a very short period of time. As the conduit supplying the motor with pressure fluid cannot, for practical reasons, have a cross-sectional area that is large enough to permit such a high speed there must be fitted a surge chamber to smooth out the intermittent fluid flow.

Moreover, owing to the large cross sectional area of the piston and the high frequency, the power output of the motor can be very high and because thereof the motor is especially suitable for driving the impacting device hereinafter described.

As being apparent from FIG. 1, the impacting device 2 consists of a hammer piston 22, a drive piston 23 intended for driving the hammer piston and an auxiliary piston 24. In this case the drive piston 23 is being constituted by the end part 8 of the motor piston 5. The drive piston 23 drives the hammer piston 22 by means of an air cushion, enclosed within a drive chamber 25 between the two pistons. This drive chamber 25 is fed with pressurized air through an inlet opening 26 which is uncovered by the drive piston in its upper end position. In this position the drive piston is spaced the largest distance from the hammer piston. During its power stroke towards the hammer piston, the drive piston covers the inlet opening 26 to define a closed chamber.

As this chamber is sealed with pressurized air the pressure therein will be multipled during power and compression stroke of the drive piston. This high pressure makes it possible to use a hammer piston having a small active area and no considerable differences in its mass cross section throughhout its length. A hammer piston having such even mass cross section throughout its length is very advantageous in that the fatigue stresses in the drill steel will be very low. Although the active area of the hammer piston is small the high pressure powertransmitting air cushion makes it possible to use a heaby hammer piston. Thus, this type of powertransmitting makes it possible to use a hammer piston having advantageous form and weight and causing less stresses in the drill steel than conventional impacting devices.

Furthermore, the impacting device 2 is provided with an annular auxiliary piston 24 surrounding the hammer piston 22 as a sleeve. The auxiliary piston 24 is in one end provided with an annular flange 27 cooperating with a flange 28 on the hammer piston. The object of the auxiliary piston 24 is to limit the return stroke of the hammer piston and to stop the hammer piston at a predetermined distance from the drive piston irrespective of the recoil energy produced by the drill steel. Hereby, the kinetic enerby of the hammer piston is absorbed by the auxiliary piston as the flanges 27 and 28 hit each other and the hammer piston is stopped in the predetermined position. As this position is critical with respect to the total impact enerby output, it is important that the hammer piston always remains in this position before the succeeding stroke.

The weight of the auxiliary piston should be about 40 percent higher than that of the hammer piston to make sure that the hammer piston will stand still after hitting the auxiliary piston.

The auxiliary piston 24 is kept in its rest position against the lower end wall 29 of the machine by pressurized air acting upon the upper end surface of the auxiliary piston. Pressurized air leaks through a clearance space between the hammer piston 22 and the housing 4 into a chamber 30 located above the auxil iary piston 24 and acts upon the upper end surface of the auxiliary piston. The space between the lower end surface of the auxiliary piston and the end wall 29 of the housing communicates with the atmosphere.

As the hammer piston 22 is driven downwardly by the drive piston 23 the following is happening. The hammer piston moves downwardly until it hits the drill steel neck (not shown). Then the hammer piston changes direction by means of the drill steel recoil on one hand and the compressed air cushion in the chamber 31 on the other hand. A considerable amount of the recoil energy of the hammer piston 22 is transmitted to the drive piston by means of the air cushion in the drive chamber 25. When the hammer piston reaches its upper direction changing position the flange 28 of the hammer piston hits the flange 27 of the auxiliary piston so that the remaining kinetic energy of the hammer piston is transmitted to the auxiliary piston. The hammer piston is thereby stopped in the predetermined position while the auxiliary piston starts to move upwardly towards the drive piston 23. The auxiliary piston is retarded and returned to its rest position by means of the air cushion in the drive chamber 30.

Owing to the powertransmitting air cushion arrangement the impacting device, according to the invention, works with a short stroke at a high frequency and performs a high impact energy output per stroke while the fatigue stresses in the drill steel are low. Fixing the start position of the hammer piston before every working stroke the auxiliary piston arrangement is also advantageous in obtaining a high total impact energy output per time unit.

FIG. 2 shows another embodiment of the invention. The machine shown is constructed with special object of reducing its length. According to this object the hammer piston has been placed within the motor piston. in other words, the motor piston is annular and surrounds the hammer piston. The manner of operation of this machine corresponds mainly with the above described machine.

The motor consists of a housing 101, an annular cylinder chamber 102 located within the housing and an annular piston 103 reciprocably guided in the cylinder chamber. Within the piston 103 is enclosed an annular chamber 104, which communicates with a pressurized air source by means of an opening 105 in the inner wall of the piston and channels 106, 107 in the housing. The conduit leading from the pressurized air source is connected to the machine by means of a nipple 108. (The machine is intended to be operated with any suitable elastic pressure fluid but to simplify the terminology it will be described with air as operating medium.) The piston 103 and the housing 101 are provided with openings 109 and 110-113 resp. and the housing is also provided with distributing channels 114-115 for distributing pressurized air to chambers at the ends of the piston causing its reciprocating movement. Futhermore, the housing 101 is provided with two exhaust openings 116 and 116".

As the piston 103 moves towards one of its end positions (the upper in FIG. 2) the following happens. At first, the piston covers exhaust opening 116 in the upper cylinder chamber. Then the openings 109 and 111 register with each other so as to let pressurized air flow from the chamber 104 within the piston, through the channel 114 to the cylinder chamber at the upper end of the piston. The cylinder chamber is then pressurized. In the next step the piston covers the opening 110 of the channel 114 closing the cylinder chamber. The piston will hereafter compress and be recoiled by the air cushion enclosed in the cylinder chamber. The piston will then start to move in the opposite direction. The channel 114 is opened by uncovering of the opening 110 whereby pressurized air may enter the cylinder chamber and drive the piston on in its new direction. In the following steps the opening 109 in the piston wall is covered by the cylinder wall and the exhaust opening 116 is uncovered by the upper edge of the piston so that the pressurized air within the cylinder chamber may escape into the atmosphere. A corresponding procedure occurs at the other end position of the piston 103.

The impacting device consists of a hammer piston 117, a drive piston 118 and an auxiliary piston 1 19. The drive piston drives the hammer piston by means of an air cushion. The drive piston 118 is constituted by a flange provided at the inner wall of the motor piston 103. The flange, as well as the motor piston, is annular and surrounds the hammer piston. The later is also provided with an annular flange 120 which cooperates with the drive piston l 18. The drive piston 118 and the flange 120 enclose an annular dn've chamber 121 in which a high pressure air cushion transmits driving drive chamber 121 constitutes a pressure riser as the drive piston compresses the enclosed air volume during its working stroke. The drive piston 118 drives the hammer piston 117 downwardly in FIG. 2 by means of the powertransmitting air cushion. Thus, the hammer piston is driving downwardly towards a drill steel neck to deliver a blow thereon. Owing to the recoil effect inherent in the drill steel and the acting pressure of the air cushion in the chamber 123 in front of the flange 120 a return movement is imparted to the hammer piston. The main part of the recoil energy of the hammer piston is transmitted to the drive piston by means of the air cushion within the chamber 121. To stop the hammer piston 117 at a distance from the drive piston which is critical with respect to the total impact energy output, the machine is provided with an auxiliary piston 119. The auxiliary piston is located at the rear end of the machine, the upper end in FIG. 2, and as it is hit by the rear end of the hammer piston it tends to to absorb the kinetic energy of the hammer piston and stop it at a predetermined distance from the drive piston. After that, the auxiliary piston gains some speed, which is retarded by the action of the pressurized air from the pressurized air source. This pressurized air acts continuously on the upper end of the auxiliary piston and returns the auxiliary piston to its rest position.

The invention is not limited to the described embodiments but can be freely varied within the scope of the claims.

In a manner usual with rock drills, the impacting devices according to the invention can be fitted with suitable drill steel chuck and drill steel rotation mechanism. What I claim is:

1. An impacting device, comprising:

a. a primary cylinder;

b. a drive piston and a hammer piston driven by said drive piston, both of said pistons being reciprocatably disposed in said cylinder;

c. a drive chamber in said cylinder between said drive piston and said hammer piston;

d. inlet means associated with said cylinder for admitting an elastic pressure fluid into said drive chamber;

e. means associated with said cylinder and said drive piston to seal said drive chamber during the power stroke of the drive piston to provide a cushion of compressed elastic pressure fluid in said drive chamber;

f. a hollow auxiliary piston reciprocatably disposed in said cylinder and accommodating said hammer piston for reciprocating movement therein;

g. a closed fluid-containing chamber defined by said cylinder, said auxiliary piston and said hammer piston permitting reciprocating movement of said pistons therein;

h. means associated with said auxiliary piston and said hammer piston effective to transmit the kinetic energy produced by the recoil movement of the hammer piston to said auxiliary piston by impact;

. said primary cylinder comprising a portion of narrowed diameter, and said drive piston having a portion of correspondingly reduced diameter forslidable engagement with said portion, said drive chamber being located within said narrowed portion of the primary cylinder at the narrowed end of the drive piston.

2. An impact device according to claim 1 in which said auxiliary piston surrounds said hammer piston providing a secondary cylinder in which the hammer piston is reciprocated.

3. An impacting device according to claim 1, in which said inlet means is an inlet port in the primary cylinder wall. 

1. An impacting device, comprising: a. a primary cylinder; b. a drive piston and a hammer piston driven by said drive piston, both of said pistons being reciprocatably disposed in said cylinder; c. a drive chamber in said cylinder between said drive piston and said hammer piston; d. inlet means associated with said cylinder for admitting an elastic pressure fluid into said drive chamber; e. means associated with said cylinder and said drive piston to seal said drive chamber during the power stroke of the drive piston to provide a cushion of compressed elastic pressure fluid in said drive chamber; f. a hollow auxiliary piston reciprocatably disposed in said cylinder and accommodating said hammer piston for reciprocating movement therein; g. a closed fluid-containing chamber defined by said cylinder, said auxiliary piston and said hammer piston permitting reciprocating movement of said pistons therein; h. means associated with said auxiliary piston and said hammer piston effective to transmit the kinetic energy produced by the recoil movement of the hammer piston to said auxiliary piston by impact; i. said primary cylinder comprising a portion of narrowed diameter, and said drive piston having a portion of correspondingly reduced diameter for slidable engagement with said portion, said drive chamber being located within said narrowed portion of the primary cylinder at the narrowed end of the drive piston.
 2. An impact device according to claim 1 in which said auxiliary piston surrounds said hammer piston providing a secondary cylinder in which the hammer piston is reciprocated.
 3. An impacting device according to claim 1, in which said inlet means is an inlet port in the primary cylinder wall. 